1. Field of the Invention
The present invention relates to an imaging apparatus, and, more particularly, to a printhead carrier vibration isolator.
2. Description of the Related Art
A typical imaging apparatus, such as an ink jet printer, forms an image onto a recording medium, such as paper or film, by causing an imaging substance to be deposited onto the recording medium. For example, an ink jet printer forms an image on a recording medium by selectively ejecting ink from a plurality of ink jetting nozzles of the printhead to form a pattern of ink dots on the recording medium. During ink jet printing, the printhead, mounted in a printhead carrier, is moved across the recording medium from one end to another in a scan direction by a carrier drive mechanism that includes a carrier belt, pulleys, and a motor. While the printhead is moving in the scan direction, ink is selectively ejected from the ink jetting nozzles to form a print swath. After completing at least one print swath, the recording medium is indexed a selected amount in a sub scan, i.e., paper feed, direction.
When the printhead is scanning across the recording medium, vibrations are developed in the printhead. These vibrations cause degradation of the image quality by producing a cyclic error that contributes to vertical banding, and is visible to the naked eye. One cause of such printhead vibration is torque ripple developed in the motor used to drive the printhead carrier back and forth across the recording medium. The torque ripple sets up vibratory modes in the carrier belt, which transfers the vibratory energy to the printhead carrier. The torque ripple, in conjunction with the carrier drive mechanism, also causes the torque of the motor to fluctuate, which produces a fluctuation in the force driving the printhead carrier, also yielding vertical banding.
Schemes for reducing such registration error have been attempted, for example, by the use of springs. However, springs alone may not provide sufficient damping to adequately absorb or isolate the offending frequency. In addition, damper inserts have been utilized, but these inserts may not provide sufficient damping at the low frequencies associated with carrier drive torque ripple. Also, some of these schemes may not provide sufficient rigidity, thereby affecting carrier drive control system response. Further, at least some of these schemes tend to involve a significant number of parts, thus increasing the cost and complexity of the printhead carrier and drive mechanism.
What is needed in the art is an apparatus for damping the vibratory modes in a printhead carrier and drive mechanism, particularly at low vibration frequencies.